this is discussed in Macbook Pro area on this site
... more thoroughly. Bottom line seemed to be.... take it back within the 14 days.
Or, with a little ultrafing sandpaper... (the white kind where you can't even see the bits) tweak one of the rubber feet a tiny bit, to get all 4 feet on the table at once.
Or, perhaps just wait. Rubber feet are soft, and will wear down over time. 3 of them may wear down to where the 4th does start contacting the table.
But this raises questions about quality control. Why would a carved aluminum slab warp? Especially a few, out of many? Not that this happened in your case... but any material has limited strength.... so if for example it were stored in a way with other heavy items pushing on it in an asymmetrical manner (as perhaps in a suitcase?)... over time those forces could warp it. Wood, metal, stone... they all can warp.
But if it happens "new" I'd guess that the possibilities to explore would include..... (1.) that particular aluminum slab had some untypical tension in it. Perhaps there's some way to tighten up the fabrication of the blank slabs that then get CNC carved. Or (2.) perhaps they need to spot these rare warped ones after they get carved. Or (3) perhaps this is a matter of excessively big tolerances in the CNC router machine tool? I think I see a bit of that in the photo, around one of the jack openings. Whatever it is, and whatever the solution is... sounds like a case for Apple's new V.P. for Quality Control!